Cardiovascular effects of experimentally-induced brain edema will be studied in conscious rats. Non-lethal cerebral infarcts surrounded by areas of brain edema will be produced by application of cooled aluminum probes to rats' skulls. Magnitude of edema will be quantified and correlated with changes in systemic arterial pressure, heart rate, stroke volume, and peripheral resistance. To allow continuous measurements of cardiovascular function in the unanesthetized state, rats with chronically implanted vascular catheters and electromagnetic flow probes will be used. By comparing responses of hypertensive rats with those of normotensive ones, the possible contribution of persistently elevated arterial pressures to the development of brain edema will be determined. Efficacy of various drugs that are used clinically for treatment of brain edema will be tested and selective pharmacologic blockade will be used to evaluate the role of sympathetic and parasympathetic nerves in the cardiovascular response to brain edema.